A battery module generally includes a plurality of cells, a pair of end plates, a pair of side plates, a base and a plurality of sleeve members. The pair of end plates and the pair of side plates are connected to each other to form a frame of the battery module, and the plurality of cells are disposed side by side within the metal frame. The sleeve member includes a sleeve and a fastening bolt. The sleeve is disposed at a corner of the metal frame and is fixedly connected to the end plate or the side plate. The fastening bolt extends through the sleeve toward the base, with the head thereof the fastening bolt abutting against the upper end face of the sleeve, and the threaded portion of the tail thereof being screwed into the base and the metal frame is fixed to the base.
The upper end face of the sleeve generally has poor flatness because of effect of an involved processing process. For example, when the sleeve is processed in a rolled manner, a convex hull is formed on the upper end face of the sleeve due to pressing stress at the time of rolling, as known from principles of mechanics. When the fastening bolt is attached to the upper end face of the sleeve, the threaded portion of the fastening bolt can't be screwed into the base along the direction of its own axis, which increases the difficulty of connecting the fastening bolt to the base, and reduces the installation efficiency. Therefore, it is necessary to propose an improved solution to solve the drawbacks described above.